Earth boring apparatus



April 1, 1958 J. J. UDRY EARTH BORING APPARATUS 4 Sheets-Sheet 1 1 Filed March 18, 1954 April 1, 1958 J. J. UDRY 2, 2

' EARTH BORING APPARATUS I Filed March 18, 1954 4 Sheets-Sheet 5 4 Sheets-Sheet 4 April 1, 1958 J. J. UDRY' EARTH BORING APPARATUS Filed March 18, 1954 ffl A United States Patent 0 EARTH BORING APPARATUS John J. Udry, Van Nuys, Calif., assignor to Borg-Warner Corporation, Chicago, Ill., a corporation of Iiliinois I Application March 18, 1954, Serial No. 417,157

7 Claims. (Cl. 2554) The present invention relates in general to earth bore drilling apparatus and more particularly to an earth borto provide an auxiliary device adapted to be utilized in conjunction with earth bore drilling apparatus of the general type disclosed in the patent to A. G. Bodine 2,554,005. T

In earth boring apparatus of the type disclosed in the aforementioned Bodine patent, suitable vibration generating mechanism is u tilizedfor generating sonic vibrations in the drill rod and bit in order to provide the necessary force to execute the drilling operation. in such drilling devices, the vibrating bit is maintained substantially in engagement with the bottom of the Well hole and the earth formation immediately adjacent to the bit is shattered either due to vibrations imparted thereto by the bit itself or due to the percussive action of the bit on the formation. In a drill of this type the bit reciprocates or vibrates vertically at very nearly the resonant vibration frequency of the massive drill rod and bit and the amplitude of the vibrations of the vibrating bit is of the order of three-sixteenths to approximately one-half inch.

As is customary in oil well drilling operations, a suitable mud fluid is pumped into the well hole, downwardly through the drill string and drill rod, with the mud fluid emerging from the bottom of the drill rod being forced out of the well hole upwardly around the drill rod and drill string andinside of the well hole. As the mud fluid rises in the well hole in this manner it takes with it the formation fragments or chips of the formation which have been broken up by the bit.

in order to efficiently utilize the energy which supplies the force forvibrating the drill rod and bit, it is necessary that the drill rod and bit be acoustically isolated from the supporting drill string and derrick. Otherwise, the energy supplied to the drill rod and bit for vibrating the same is dissipated in the form of acoustic vibrations or waves which travel to the surface through the drill string and derrick. As a practical matter, when the vibrating drill rod and bit are not substantially acoustically isolated from the supporting drill string, the vibrations travel up the drill string and proceed to set the derrick in vibration at frequencies and amplitudes suficiently high to shake loose any partially loosened parts thereof. 'As is apparent, if a. boltor other article is shaken loose from the top of the derrick and falls downwardly, there is a definite hazard to the persons operating the drilling rig.

The principal object of the present invention is therefore to provide a device for acoustically isolating an acoustically vibrating drill rod and bit from the supporting drill string and derrick.

uously lower the supporting drill string.

acoustically vibrating drill rod and bit and the supporting drill string whereby the bit may be held against the earth formation at the bottom of the well hole by a substantially constant force under all practical operating conditions.

A further object of the present invention is to provide a lost motion connection between a sonically vibrating drill rod and bit andthe supporting drill string therefor, to thereby enable the operator of the drilling rig to more easily control the drilling operation by making it possible for the drill rod and bit to travel continuously downwardly as the earth formation is shattered at the bottom of the well hole without the operator having to contin- In this connection, the lost motion connection between the drill string and drill rod affords relative sliding movement of the order of twenty inches to two feet so that it is necessary for the drilling rig operator to lower the supporting drill string only when the bit has penetrated the earth formation by approximately this amount. Of course, due to the type of formation being drilled, the speed of penetration of the bit will vary and, accordingly, the

frequency with which the operator must incrementally lower the drill string will vary.

7 A further object of the present invention is to provide a lost motion connection between a drill rod and the supporting drill string which is efliective to acoustically isolate the drill rod from the drill string at all times.

A further object of the present invention is to provide an acoustic isolator between a drill rod and its supporting driil string comprising a keyed connection between the drill rod and drill string for causing them to rotate in unison and permitting them to have relative sliding movement and including a resilient coupling means between the drili rod and drill string for isolating the drill string from vibrations in the drill rod.

Another object of the present invention is to provide an acoustic isolator between a drill string and a vibratory drill rod wherein one of the members is telescopically received within the other and each of the members is provided with an abutment affording lost motion therebetween for acousticallyisolating the members when the drill rod rests entirely on the earth formation at the bottom of the well hole, and there being a compression spring means disposed between the abutments on the members for effecting a resilient connection between the abutments when the drill rod has penetrated the earth sufiiciently deep to take up all of the free lost motion.

riefiy, the present invention contemplates providing a pin member at the upper end of the drill rod adapted to be telescopically received within a generally elongated cylindrical portion formed at the bottom end of the drill string. Suitable .abutments are formed on each of the members which provide a lost motion connection between the drill rod and drill string and which lost motion connection is effective to acoustically isolate the drill rod from the drill string. Compression spring means are disposed between said abutments and have sufficient strength to support the entire mass of the drill rod when it is hanging free without having the convolutions of the compression spring means engage each other. A a result, the drill rod is acoustically isolated from the drill string even when substantially the entire mass of the drill rod is supported by the drill string. The acoustic isolator provided by the present invention is particularly desirable in that it is simple and may be composed ofrugged parts,

the compression spring means being substantially the only part thereof which is subjected to great forces for any extended period of time.

A further detailed object of the present invention is to provide a lubricated pilot bearing suitable for use in an acoustic isolator of the type disclosed herein for maintaining concentric alignment between the telescopically in the space betweenthe bushings is filled with a lubricant and one of the bushings is adapted to have an external fluid pressure applied to an outside end thereof for thereby tending to compress the bushings toward each other for placing the lubricant between the bushings under pressure substantially equal to the external fluid pressure.

Another object of the present invention is to provide a pilot bearing suitable for use between the supporting sub of an oil well drill string and the upper sub of an acoustically vibratory drill rod, which pilot bearing comprises a pair of longitudinally spaced bushings which define a lubricant chamber wherein at least one of the bush ings is adapted to have the mud fluid, which is used for driving the drill and removing the formation fragments from the bore hole, act on one end of the bushing for placing the lubricant in the chamber between the bushings under pressure substantially equal to the pressure of the mud fluid.

The present application is concerned chiefly with the features of the disclosed pilot bearing and lubricator and it is these features to which the claims herein have been directed. The general features of the acoustic isolator and the constructional details of the improved kelly and of the device for removing coarse abrasive particles from the mud fluid have been disclosed and described in detail herein in order to provide a better and more thorough understanding of the present invention. However, each of these features has been made the special subject of other copending patent applications filed of even date herewith. The general features of the acoustic isolator are disclosed fully and claimed in the copending application of H. V. D. Stewart, Ser. No. 417,117, filed March 18, 1954, now abandoned. The improved kelly or torque transfer unit I is fully disclosed and claimed in the copending application of H. V. D. Stewart, Ser. No. 417,118, filed March 18, 1954. The device for removing coarse and abrasive particles from the mud fluid is disclosed fully and claimed in the copending application of J. P. Selberg and J. .l. Udry, Ser. No. 417,092, filed March 18, 1954, now Patent No. 2,800,301.

The foregoing and numerous other objects and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings, wherein:

Fig. l is a view showing a typical installation of an oil well drilling apparatus showing the surface equipment and the drill string extending down into the well hole, with the drill rod and bit not. being shown in this figure;

Fig. 2 is a view showing the drill rod and bit of the type disclosed in the aforementioned Bodine patent the posed in a well hole with the bit resting on the bottom of the well hole;

Fig. 3 is a view similar to Fig. 2 but shows the drill rod and bit suspended by the drill string with the bit hanging free in the well hole, the entire mass of the drill rod being supported by the drill string;

Figs. 4A, 4B and 4C, when assembled with Fig. 4A above and Fig. 4C below Fig. 4B, disclose on a somewhat enlarged scale, the acoustic isolator comprising the subject matter of the present invention;

Figs. 5A, 5B and 5C, each disclose fragmentary sectional views of portions of the acoustic isolator, Fig. 5A disclosing the pilot bearing and lubricator for the pilot bearing at the upper end of the isolator; Fig. 5B disclosing the lost motion connection between the drill string and drill rod with the compression spring means disposed bei tween abutments respectively formed on the drill string and drill rod and Fig. 5C disclosing the slidable driving connection between the drill string and drill rod near the bottom of the isolator;

Fig. 6 discloses a sectional view of the slidable driving connection between the drill string and drill rod and is taken substantially along the line 66 in Fig. 5C and looking in the direction of the arrows; and

Figs. 7 and 8 comprise enlarged detail views of the pilot bearing and lubricator for the pilot bearing; Fig. 7 comprising a view similar to that shown in Fig. 5A and Fig. 8 showing the lubricator cavity compressed due to escape of lubricant therefrom.

Referring now to the drawings wherein like reference numerals have been used in the different views in order to identify identical parts and with particular reference to Fig. 1, the equipment disposed on the surface of the earth above the well hole will first be described. This equipment is conventional and includes derrick 10, draw works 11, driving rotary table 12, kelly 13 extending through table 12, swivel 14 coupled to the upper end of the fluid passage through kelly 13 and book 15 supporting the bail of swivel 14. The hook 15 is suspended by means of a traveling block 16 and cable 17 extending from the top of the derrick 10 and the cable 17 is wound on the usual hoisting drum of the draw works 11. Mud fluid, such as is conventionally employed in rotary oil well drilling operations, is pumped through a supply line 18 from a supply tank or sump 19 and is delivered under pressure by a pump 20 through a pipe 21 and hose 22 to the gooseneck of swivel 14, and .from this point the mud fluid flows down through the kelly 13 and through a drill pipe string 23 coupled to the lower end of the kelly 13.

The kelly 13 and the drill string 23 extend into a bore hole 24 which extends downwardly into the earth. The bore hole 24 is lined for a suitable distance down from the ground surface by surface casing 25 which is sup- 7 ported by a landing flange 26 resting on a concrete footing 27 in the bottom of a pit 28. A blow-out preventer 29 is mounted at the head of the casing 25 and a riser 30 above the blow-out preventer 29 is provided with a mud flow line 31.' The mud flow line or delivery pipe 31 is shown as discharging to a conventional vibratory mud screen 32, and the mud is returned from the latter back to the sump 19 by means of a pipe line 33.

The drill pipe string 23 coupled at the lower end of the kelly 13 comprises a conventional drill pipe string and it will be understood that this drill string is made up of a number of usual drill pipe lengths coupled together by the usual tool joints (not shown).

The drill string 23 suspends a drill rod 34 in the well hole 24, the drill rod 34 being coupled to the drill string 23 by means of an acoustic isolator, indicated generally by reference numeral 35. Fastencd to the drill rod 34, at the upper end thereof is a turbine 36 and a vibration generator assembly or oscillator 37, both of which are of the type disclosed in the aforementioned patent to Bodine 2,554,005. It is not essential for a thorough understanding of the present invention to describe the turbine 36 and vibration generator assembly 37 in detail herein as the details of operation and construction of the turbine and vibrator are set forth in full in the aforementioned Bodine patent. It will suffice to state herein that the turbine 36 and vibrator 37 are capable of vibrating the drill rod 34 and a bit 38 secured at the lower end of the drill rod at a frequency approximately equal to the reso nant vibration frequency of the drill rod and bit.

The drill rod 34, in addition to the turbine 36 and vibrator assembly. 37 includes a massive elongated elastic longitudinally vibratory rod which is of substantial mass and length. This drill rod 34 may be made up of a plurality of steel drill collars, which are connected together preferably by means of tool joints of the pre-stressed type, such as is disclosed in the copending application of Udry et al., Ser. No. 394,432, filed November 25, 1953. It is contemplated that the lowermost drill collar of the drill rod 34 will. be provided with an acoustic or sonic decoupler cell such as is disclosed in the copending application of Currieet al. Ser. No. 360,706, filed June 10, 1953, now Patent No. 2,771,270. No further description of the decoupler cell will be given herein as the complete details thereof are set forth in said Currie et al. application. Immediately beneath the decoupler cell, the bit 33 is disposed and it is not considered necessary for a thorough. understanding of the present invention to describe in detail the construction of the bit 38.

Referring now to Figs. 4A, 4B, 4C, 5A, 5B and SC in particular, the constructional details of the acoustic isolator and of the pilot bearing and lubricator therefor comprising the subject matter of the present invention will now be described.

The drill string 23 has a lowermost drill collar which is coupled to an upper isolator sub 53 by means of a pre-stressed joint 54 of the type disclosed in the aforementioned Udry et al. application Ser. No. 394,432. The upper isolator sub 53 is coupled'to a lower'isolator sub 55 by means of a similar pre-stressed joint 56.

The upper end of the drill mass comprises a hollow pilot sub 57 which has a substantially cylindrical outer periphery adapted to slide within a pair of lubricated bushings 58 and 59 in order to pilot the drill rod 34 within the lower end of the drill string 23. The hollow pilot sub 57 is rigidly coupled to a short adapter sub 60, these two subs being retained rigidly secured together by any desired means, such as welding indicated at 61. The short adapter sub 60 is coupled to a main internal isolator sub 62 by means of a joint indicated generally by reference numeral 63. The joint 63 includes mating tapered surfaces 64 and 65 respectively formed on the adapter sub 6%) and on the isolator sub 62 and also includes mating threaded portions 66 and 67 respectively formed on the inner periphery of the lower end of the adapter 6'!) and on the outer periphery of the isolator sub 62. An O-ring 63a is disposed within a suitable peripheral groove formed in the interior surface of the adapter sub as and is effective to provide a seal between the adapter sub 60 and the internal isolator sub 62.

The joint 63 may also be pre-stressed by relatively turning the mating threaded portions 66 and 67 until the portions of the adapter sub 6t) and isolator sub 6?; between the threaded regions and tapered regions thereof are respectively pre-stressed in tension and compression. This is effective to insure that the joint 63 will remain tight while the drillrod 34 is vibrated by the vibration generator assembly 37.

The hollow isolator sub 62 is coupled to a hollow torque transfer sub 68 by means of a pro-stressed joint 69 of the type disclosed in the copending Udry et al. application Ser. No. 394,432. The pre-stressed joint 69 is pinned by means of a pin on slug 7G in order to insure against. this joint loosening as a result of vibrations induced in the drill rod 34 by means of the turbine 36 and vibration generator assembly 37. An O-ring 6% disposed in a suitable groove formed'in exterior periphery of torque transfer sub 68 provides a seal between the isolator sub and the torque transfer sub 63.

It will be noted that the upper isolator sub 53 is quite thin for a considerable longitudinal distance and telescopically disposed within the upper isolator sub 53 is the thin internal isolator sub 62 ofthe drill rod 34. The radially spaced inner surface 7.l of the sub 53 and outer surface 72 of the sub 62 provide an annular cavity 73 for receiving compression spring means, indicated generally by reference numeral 7d, therebetween.

The longitudinal extent. of the annular cavity 73 is defined by a pair of abutment stops comprising an upper abutment stop 75 havin internal threads 76 adapted to be threaded onto the externally threaded portion 67 of the internal isolator sub 62 and a lower abutment stop 77 on the sub 55. The abutment stop 75 serves as a lock nut when it is screwed onto the threads 67 until it tightly abuts the lower end of the adapter sub 60. The lower end of the annular cavity 73 is defined by the abutment stop 77 which is received within the upper ,end of the lower isolator sub 55. The abutment stop 77 has a flange 78 adapted to seat upon the upper end of the lower isolator sub 55.

The compression spring means 74 disposed within the annular cavity '73 comprises a pair of compression springs 79 and 86 having a stiff separating washer 81 disposed therebetween.

When the drill is disposed in the bore hole 24 and the bit 31% is disposed against the earth formation at the bottom of the hole, the relative positions of the drill rod 34 and drill string 23 are as shown in Fig. 2 of the drawings. In other words, so long as the drill bit 38 rests upon the formation at the bottom of the bore hole 2 3, there is considerable space in the annular cavity 73 above the compression spring means 74 and below the abutment stop 75. When the drill rod 34 hangs suspended in the bore hole 24, with the bit 38 held above the formation at the bottom of the bore hole, the entire mass of the drill rod 34; is suspended by the compression spring means 74. This latter condition is disclosed in Pig. 3 of the drawings. The compression spring means 74 are sulficiently strong to support the entire mass of the drill rod 34, for so long as it hangs free, without causing the compression springs 79 and 8b to compress to the point where the successive convolutions thereof rest upon each other. It is therefore apparent that under all conditions of operation the drill rod 34 is never rigidly coupled to the drill string 23 and thus it may be said that the drill string 23 is acoustically isolated from the vibratory massive drill rod 34.

In the operation of an earth boring drill of the general type disclosed herein, it has been found desirable to rotate the drilling bit as the boring operation progresses. This is due to the fact that when the bit 38 is not rotated as it is vibrated it tends to become locked in. the formation at the bottom of the bore hole 24. The acoustic isolator 35 therefore includes means for transferring torque from the supporting rotary drill string 23 to the massive-elongated drill rod 34. This torque transfer unit will now be described.

The torque transfer unit for coupling the drill string 23 for rotation in unison with the drillrod 34 is indicated generally by reference numeral 82. The torque transfer unit 82 comprises a sleeve 83 secured rigidly to the lower isolator sub 55 by any convenient means, such as welding for example, and provided with a plurality of semicylindrical openings 84 for snugly receiving an equal number of longitudinally extending pins 85. The converging sides 86 and 87 of each of. the openings 84 serve to hold each of the pins in the openings 84. The openings 84 are so located in the sleeve 83 that the pins 85 each project inwardly beyond the inner periphery 88 of the sleeve 83.

A short abutment sub 89 is rigidly secured to the sleeve 83 by means of a plurality of screws 99 which extend through suitable openings in flanges 91 formed on the upper end of the abutment sub 89 and which extend into suitable threaded openings 92 formed in the sleeve 83. The flanges 9.1 on the upper end of the abutment sub 89 are also provided with a plurality of threaded apertures 93 for receiving suitable short set screws or locking screws 94 which may be turned until they reach the ends of the pins 85 for thereby holding the pins 85 in longitudinally fixed relation in the sleeve openings 84. The lower end of the abutment sub 89 comprises an annular fiat surface.95 adapted to abut van'upper flat surface 96 formed on the upper end of the uppermost drill collar of the drill rod 34. The annular abutment sub 89 is adapted to rest upon the surface 96 of the drill rod 34 only when the entire mass of the drill string 23 is resting upon the formation at the bottom of the earth bore 24.

The torque transfer unit 82 also includes the hollow torque transfer sub 68 which is provided with a plurality of longitudinally extending grooves 97. A groove 97 is provided for each corresponding pin 85, with each of the grooves 97 comprising a semi-cylindrical cavity formed in the torque transfer sub 68 and formed with a slightly greater radius of curvature than the radius of curvature of the torque transfer pins 85. In the operation of the present drilling apparatus the sleeve 83 is adapted to rotate in a clockwise direction, as indicated in Fig. 6, and the pins 85 serve as keys, when seated within the openings 97, for transferring torque from the sleeve 83 to the hollow torque transfer sub 68. In order to minimize wear on the sides of the grooves 97, each of the grooves 97 in the hollow torque transfer sub 68 is provided with a hard metal insert 98 made of some substantially wear-resistant material. Therefore, as the sleeve 83 turns in a clockwise direction, the pins 85 strike the wear-resistant inserts 98 and thus wear on the sides of the grooves 97 is held to a minimum.

Because of the fact that the grooves 97 are slightly larger than the pins 85, there is some freedom between the pins 85 and the defining walls of the grooves 97. This space provided by the freedom between the sides of the grooves and the pins 85 affords suitable passages for the passage of mud fluid between the grooves and pins, which mud fluid serves to cool these parts of the torque transfer unit which would otherwise heat up considerably due to friction between the pins 85 and inserts 98. The friction between the pins 85 and inserts 98 is considerable inasmuch as the drill rod 34 and hollow torque transfer sub 88 are vibrating at substantially the resonant vibration frequency of the drill rod 34 simultaneously with rotation of the torque transfer unit 82. 'Thus it is apparent that the friction between the pins 85 and the inserts 98 is of such a magnitude as to make it desirable to convey away the heat, generated by the friction, as rapidly as possible. It has been found that by providing the enlarged grooves 97, the mud fluid, which serves to provide the force or power for actuating the drill rod 34 and bit 38 as well as to provide the force for removing the chips of the formation which are broken away at the bottom of the earth bore by means of the bit 38, is also effective to cool the torque transfer unit.

Even though there is sufficient play of the pins 85 in the grooves97 for mud fluid to pass through the grooves 97 in order to cool the torque transfer unit, the torque transfer unit 82 is effective in maintaining the drill rod 34 and drill string substantially concentric with respect to each other at the lower end of the acoustic isolator 35. Due to the rather extreme forces which act upon the drill rod 34, it is essential that the uppermost end of the drill rod 34 also be maintained in concentric alignment within the lower end of the drill string 23. The means for maintaining the upper end of the drill rod 34 in'concentric alignment with the drill string 23 will now be described.

The two bushings 58 and 59 comprise pilot bearings disposed between the inner periphery of the drill collar 50 and'the outer periphery of the hollow pilot sub 57. Both bushings 58 and 59 are designed so as to flt rather snugly within the inner surface 99 of the drill collar 50, but there is freedom for the isolator sub 57 to slide longitudinally or reciprocate within the inner peripheries 100 and 101 of the bushings 59 and 58 respectively.

The bushing 59 is held fixed with respect to the drill collar 50 by means of an inwardly projecting shoulder 102 formed on the inner periphery of the drill collar 50 and by means of an abutment or stop washer 103 disposed in a suitable groove formed on. the inner periphery of the drill collar 50. Upward movement of the bushing 58 with respect tov the drill collar 50 is limited by an abutment or stop washer 104 mounted in a suitable groove in the inner periphery of the drill collar 50. However, the bushing 58 is free to move downwardly with respect to the drill collar 50. Each of the bushings 58 and 59 are provided with internal peripheral grooves 105. Radial openings 106 formed in each of the bushings 58 and 59 communicate with the peripheral grooves and a plurality of longitudinal passages 107 establish communication from an annular cavity 108, comprising the space between each of the bushings, to the internal peripheral grooves 105 formed in each of the bushings 58 and 59.

Each of the bushings 58 and 59 is respectively provided with a pair of O-rings 109 and 110, the O-rings 109 being provided for sealing the bushings 58 and 59 with respect to the drill collar 50 and the O-rings 110 being eifective to provide a seal between the inner peripheries of the bushings 58 and 59 and the outer periphery of the hollow pilot sub 57. The drill collar 50 is provided with a radially extending opening 111 for facilirating filling the cavity 108 with a suitable heavy lubricant or grease. A valve 112 provided at the outer end of the radial opening 111 is adapted to open when lubricant is to be forced into the cavity 108 and to automatically close so as to prevent the escape of lubricant from the cavity 108 through the opening 111. The bushing 58 is provided with a longitudinally extending passageway 113 having a check valve 114 provided at the inner end thereof, which check valve is adapted to open in the direction of fluid escape from the cavity 108.

When the cavity 108 is being filled with fluid lubricant or grease it is forced under pressure into the cavity through the valve 112. Fig. 8 shows the cavity 108 when partially filled with lubricant. Air from within the cavity 108 is free to escape through the passageway 113 and through the check valve 114. Since it is contemplated that the fluid lubricant admitted into the cavity 108 through the valve 112 will be rather heavy, such as a grease, for example, it will be readily apparent that the cavity becomes filled due to the escape of the fluid lubricant through the passageway 113. Due to the fact that the escape passageway 113 is small and since the bushing 58 fits quite snugly within the inner periphery 99 of the drill collar 50 and due to the further fact that the fluid lubricant admitted into the cavity 108 is heavy, the bushing 58 will tend to remain in the position shown in Figs. 5A and 7 and the cavity 108 will remain filled. When the acoustic isolator 35 is lowered into the earth bore hole 24 and mud fluid is pumped downwardly through the drill string 23 and drill rod 34, the pressure of the mud fluid is exerted on the upper end of the bushing 58 and on the check valve 114. The mud fluid pres sure thus closes the check valve 114 and the bushing 58 tends to be compressed toward the bushing 59 so as to place the fluid lubricant within the cavity 108 under pressure substantially equal to the pressure of the mud fluid. Subsequently, as the pressure of the mud fluid varies, it will exert a corresponding variable pressure on the upper end of the bushing 58 so that the pressure of the fluid lubricant within the cavity 108 at all times remains substantially equal to the pressure of the mud fluid acting on the bushing 58.

The fluid lubricant in the cavity 108 communicates with the internal bushing surfaces 101 and 100, in order to maintain the outer surface of the pilot sub 57 lubricated, through the passageways 107 and 106 leading to the internal peripheral grooves 105. The O-ring seals 109 and 110 substantially seal the cavity 108 and since the pressure of the mud fluid outside of the cavity on the end of the bushings 58 and 59 is substantially the same as the pressure of the fluid lubricant, there is little tendency for there to be any escape of the fluid lubricant through or around the O-ring seals 109 and 110.

Figs. 7 and 8 show the relative positions of the upper sleeve bushing 58 when the cavity is enlarged to its full volume and when the cavity is decreased in size due to compression of the bushing 58 toward the bushing 59. During the operation of the. drill there will be some lubricant leakage out of the lubricant cavity 108, but since the bushing 58 is capable of moving downwardly (see Fig. 8) under the pressure of mud fluid acting against the outside end thereof, the lubricant pressure within the cavity 108 remains substantially equal to the mud pressure acting on the bushing '58.

In order to insure against having large fragments of abrasive material reaching the mud turbine 36, means are provided in the acoustic isolator 35 for removing such large fragments from the stream of mud fluid and this means will now be described. At the upper end of the hollow pilot sub 57 a cap 115 is provided. The cap 115 is secured to the end of the pilot sub 57 by any well known or desired means, such as welding for example, and the cap is adapted to be disposed in substantial concentric relation within the lowermost sub 116 of the drill string 23. The cap 115 is provided with a semi-spherical leading end 117 for deflecting the mud fluid outwardly toward the inner periphery of the sub 116. The cap 115 is also provided with a plurality of elongated slots extending longitudinally with respect to the cap 115, the elongated slots in the cap 115 having been designated by reference numeral 113. The hollow pilot sub 57 is disposed in substantial concentric relation within the lower end of the drill string sub 116 and an annular cavity 119 exists between the sub 116 and pilot sub 57. This annular cavity 119 extends fromthe lower end of the cap 115 downwardly to very near the end of the sub 116 where the inner periphery of the sub 116 is necked in, as indicated at 120. There is sufficient freedom between the necked-in portion 126 of the sub 116 and the outer periphery of the pilot sub 57 so that the mud fluid entering the cavity 119 may communicate with the upper end of the bushing 58. It will thus be seen that full mud pressure is applied to the upper end of the bushing 58 so as to cause this bushing to act like a piston against the lubricant disposed in the lubricant cavity 108.

Mud fluid passing downwardly "through the drill string 23, for the purpose of driving the turbine 36 and carrying away chips of the formation broken away from the bottom of the bore 24 by the action of the bit 38, passes downwardly through the lowermost drill collar 1160f the drill string 23 and upon reaching the cap 115 is deflected by means of the semi-sphericalleading end 117 of the cap 115 toward the shell of the sub 116. -In order for the mud fluid to proceed downwardly through the drill rod 34 it must pass through the openings 118 in the cap 115. it will thus be seen that the direction of flow of the mud fluid, as it is deflected by the semispherical end 117 of the cap 115 and thereafter passes into the pilot sub 57 through the slots 118, is changed considerably. Since the mud fluid is largely made of fine mud particles retained in suspension in the fluid, the mud fluid flows readily through this meandering path. The heavy or coarse abrasive particles do not so readily adjust themselves to the changes in direction of mud fluid flow and therefore when the heavy or coarse fragments are deflected outwardly by the cap 117 they tend to settle between the cap. 115 and the sub 116 into the cavity 119. Therefore, the coarse or heavy frag ments which would abrade the blades of the turbine 36 are prevented from ever reaching the turbine since they settle into the cavity 119 and remain therein.

In order to facilitate removing the mud fluid and the settled coarse fragments from the cavity 119, a pair of plugs 121, which may be removed, are provided. The mud fluid may then be washed out through the holes provided when the plugs 121 are removed.

In order to permit and insure the free longitudinal vibratory and reciprocatory movement of the drill rod 34, the isolator subs 53 and 55 are each provided with a plurality of radial openings 122. During downward movements of the drill rod 34 the volume of the annular cavity 73 increases and by permitting the mud fluid from outside of the isolator sub 53 to enter the cavity 73 there is no tendency for there to be a vacuum created within the cavity 73 as the drill rod 34 moves downwardly. Likewise, when the drill rod 34 moves upwardly relative to the two isolator subs 53 and 55, the volume of the cavity 7 created between the drill rod 34 and the drill string. The

openings 122 in the lower isolator sub 55 also facilitate the passage of mud fluid into and out of the space between the lower isolator sub 55 and the hollow torque transfer sub 68. It will be recalled that it is desirable that some mud fluid pass between the pins and the peripheries of the grooves 97 in the torque transfer unit 82 in order to provide cooling of the pins 85 and metal inserts 98. The mud fluid, as stated previously, may pass downwardly through the grooves 97 and thereafter may escape to the outside of the drill rod by passing between the inner periphery of the abutment sub 89 and the outer periphery of the torque transfer sub 68 and thence outwardly between the abutment surfaces 96 and 95.

In the operation of the drilling apparatus of the type disclosed herein, the drill string 23 and suspended drill rod 34 are gradually lowered into the earth bore 24 until the bit 38 strikes the bottom of the bore 24. While the drill string 23 and drill rod 34 are being lowered into the earth bore 24, the relative positions of the drill string 23 and drill rod 34 are as disclosed in Fig. 3, with the entire mass of the drill rod 34 being supported by the compression spring means 74. The drilling rig operator will permit the drill string 23 to descend until the bit 38 strikes the formation at the bottom of the bore hole 24 and will permit the drill string 23 to descend thereafter until the abutment surfaces 94 and 96 are almost in engagement. At this time there will be some twenty to twenty-four inches existing between the top of the upper compression spring'79 and the bottom of the abutment stop 75.

The actual drilling operation is then commenced. Mud fluid is pumped by the pump 20 downwardly through the drill string 23 in order to-drive the turbine 36. The turbine 36 actuates the oscillator 37 and the drill rod 34 is thus set into longitudinal vibration. The vibration of the drill rod 34 is at substantially the resonant vibration frequency .thereof. The bit then commences to break up the formation at the bottom of the bore hole 24 and the drill rod 34 descends, the abutment stop 75 moving downwardly at this time toward compression spring 79. The drilling rig operator will permit the drill rod 34 to descend relative to the drill string 23 for a distance of the order of approximately one and one-half feet. Throughout this entire penetration of the bit 38 into the formatron, the vibratingdrill rod 34 is acoustically isolated from the suporting drill string 23 since the abutment stop 75 at no time even engages the spring 79 due to the fact that the entire mass of the drill rod 34 is resting on the bottom of the formation in the bore hole 24.

The drilling rig operator will then permit the drill string 23 to descend approximately one and one-half feet until the stops 95 and 96 are just free of one another. The entire procedure is then repeated. It will therefore be apparent that the work of the drilling rig operator is greatly facilitated as a result of the fact that he does not have to maintain a continuous watch on the descent of the drill string 23. In other words, the drilling rig operator may permit the drill string 23 to descend about one and one-half feet every half minute to one and one half minutes depending upon the rate of penetration of the drill into the earth.

If the drilling bit 38 penetrates the formation very rapidly, so that the relative positions of the drilling rod 34 and drill string 23 are like that disclosed in Fig. 3, the entire mass of the drilling rod 34 will be supported by the drill string 23 through the medium of the compression spring means 74. Assuming that the mud fluid continues to be pumped downwardly through the drill string so that the turbine 36 is continually operated, the massive drill rod 34 will continue to vibrate. The compression spring means 74 between the abutment stops 75 and 77 is effective to isolate the drill string 23 from the drill rod 34, even though the entire mass of the drill rod 34 is supported by the compression spring means 74. As a result, vibrations in the drill rod 34 are not transmitted to the drilling string 23 and derrick even when the mass of the drill rod 34 is entirely carried by the drill string 23.

It is therefore apparent that the present invention provides an eflicient acoustic isolator between the telescopically arranged outer supporting drill string sleeve shaft and inner vibratory drill rod sleeve shaft of an earth bore drilling apparatus and by also providing the elongated cavity 73, affording lost motion between the stops 75 and 77 the work of the drilling rig operator is facilitated inasmuch as he does not have to maintain such a diligent watch on the penetration rate of the drill bit 38. By providing the unique kelly or torque transfer apparatus 82, rotation of the drill string 23 is readily transmitted to the drill rod and wear of the different parts is held to a minimum. The unique piloting means for the telescoping drill string and drill rod sleeve shafts comprising the sleeve bushings 58 and 59 is very important since it is essential that the drill rod be maintained in concentric alignment with the drill string. Further, the means for lubricating the hearing surfaces of the pilot bearing is considered to be unique.

The cap 115 for deflecting the mud fluid to thereby facilitate settling of the coarse abrasive fragments in the mud fluid into the cavity 119is also an important and desirable feature of the present invention.

The location of the torque transfer unit 82 below the acoustic isolating compression spring means 74 is considered to be very beneficial. By locating the torque transfer unit at a point below the isolating springs, it is therefore possible to utilize a pilot sub of small diameter and cross section and to utilize isolator subs of small cross section since they do not transfer torque loads. The pilot sub and all of the sections extending therefrom up to the cap 115 are subjected, in the main, only to tension loads and in designing these portions of the drill it is not necessary to consider torsion fatigue. Since the pilot sub need be of only a small diameter the problem of finding space for locating the isolator compression springs 74 is obviously simplified.

Another advantage of the present acoustic isolator arises from the fact that the isolating compression spring means is disposed between the torque transfer unit and the pilot bearing. It is thus possible to provide the greatest possible length between the pilot bearing and the torque transfer unit and this increases the stability of the internal isolator sub 62.

Another advantage afforded by the present acoustic isolator results from the fact that the outer isolator housing is composed of an upper and a lower isolator sub so that it is not necessary to handle a long heavy sub when the apparatus is being transported. Further, by providing the internal isolator sub 62 separate from the internal hollow torque transfer sub 68, ease of handling is also facilitated and further, it is only necessary that the pilot sub be made of the highest quality steelhaving good hearing qualities. The use of the coil type compression springs renders the isolating unit practically fool-proof and maintenance is reduced to a minimum. Due to the fact that the compression spring means 74 are actually in operation only a very small percentage of the time that the drilling is actually taking place, the life of the isolating springs 74 is greatly increased.

From the foregoing description of the present invention it will be apparent that it provides an acoustic isolator adapted for use in'an earth bore drilling apparatus having a longitudinally vibratory drill rod, which acoustic isolator is simple and effective and requires a minimum of effort in order to maintain the same in proper working order. it is contemplated that numerous changes and modifications may be made in the present invention without departing from the spirit or scope thereof.

What is claimed is:

l. A pilot bearing adapted for use between a pair of telescoping sections of the drill string of an earth bore drilling apparatus wherein one of the sections vibrates longitudinally relative to the other and the drill string is adapted to have mud fluid forced downwardly therethrough and upwardly between the drill string and the inner periphery of the earth bore in order to carry away chips of the earth formation at the bottom of the bore and cut away by the drilling apparatus, said pilot hearing comprising a pair of longitudinally spaced bushings reciprocable relative to each other and disposed between said telescoping sections, said bushings surrounding the inner telescoping section and being in sealing engagement with the outer periphery of said inner telescoping section and in sealing engagement with the inner periphery of the outer telescoping section and said bushings being adapted to be movable relative to said telescoping sections while still maintaining the sealing relationship therewith whereby said bushings isolate the space between said bushings and said telescoping sections from the area above and below the respective bushing to form a lubricant chamber between said telescoping sections, lubricant disposed within said chamber, each of said bushings having one end exposed to and in communication with the mud fluid and thereby being adapted to have the mud fluid act against the respective exposed ends thereof for compressing the bushings against the lubricant disposed in said chamber for maintaining the pressure of the lubricant at substantially the same value as the pressure of the mud fluid, and a pressure relief valve for said chamber for permitting escape of lubricant therefrom in the event that the pressure of the lubricant in the chamber exceeds the pressure of the mud fluid by more than a predetermined amount.

2. A pilot bearing adapted for use between a pair of telescoping sections of the drill string of an earth bore drilling apparatus wherein one of the sections vibrates longitudinally relative to the other and the drill string is adapted to have mud fluid forced downwardly therethrough and upwardly between the drill string and the inner periphery of the earth bore in order to carry away chips of the earth formation at the bottom of the bore and cut away by the drilling apparatus, said pilot hearing comprising a pair of longitudinally spaced bushings disposed between said telescoping sections, said bushings surrounding the inner telescoping section and being in sealing engagement with the outer periphery of said inner telescoping section and in sealing engagement with the inner periphery of the outer telescoping section and said bushings being adapted to be movable relative to said telescoping sections while still maintaining the scaling relationship therewith whereby said bushings isolate the space between said bushings and said telescoping sections from the area above and below the respective bushings to form a lubricant chamber between said telescoping sections, lubricant disposed within said chamber, each of said bushings having one end exposed to and in communication with the mud fluid and thereby being adapted to have the mud fluid act against the respective exposed ends thereof for compressing the bushings against the lubricant disposed in said chamber for maintaining the pressure of the lubricant at substantially the same value as the pressure of the mud fiuid, and a pressure relief valve for said chamber and adapted to have the mud fluid act thereagainst for closing the valve whereby the valve opens readily to permit the escape of air and bubbles when the chamber is being filled with lubricant 13 and the mud fluid acts to hold the valve closed to prevent the escape of lubricant from the chamber except when the lubricant pressure exceeds the mud fluid pressure by a predetermined amount.

3. A pilot bearing adapted for use between a pair of telescoping sections of the drill string of an earth bore drilling apparatus wherein one of the sections vibrates longitudinally relative to the other and the drill string is adapted to have mud fluid forceddownwardly therethrough and upwardly between the drill string and the inner periphery of the earth bore in order to carry away chips of the earth formation at the bottom of the bore and cut away by the drilling apparatus, said pilot bearing comprising a pair of vertically spaced sleeve bushings disposed between said telescoping sections, said bushings surrounding the inner telescoping section and being in sealing engagement with the outer periphery of said inner telescoping section and in sealing engagement with the inner periphery of the outer telescoping section whereby said bushings isolate the space between said bushings and said telescoping sections from the area above and below the respective bushings to form a lubricant chamber between said telescoping sections, the lower of said sleeve bushings being fixed with respect to one of said telescoping sections, the upper of said sleeve bushings being reciprocable with respect to said telescoping sections while still maintaining the sealing relationship therewith and said one section having stop means for limiting displacement of the upper sleeve bushing from said lower sleeve bushing, the mud fluid being in communication with and acting against the upper end of said upper sleeve bushing whereby the upper sleeve bushing acts as a piston for pressurizing the lubricant within said chamber at a value substantially equal to the pressure of the mud fluid for thereby minimizing leakage of the lubricant from said chamber, and a pressure relief valve disposed in one of said sleeve bushings for relieving the lubricant pressure in said chamber and adapted to have the mud fluid act thereagainst for closing the valve at all times except when the lubricant pressure exceeds the mud fluid pressure by more than a predetermined amount.

4. A pilot bearing for maintaining the concentric alignment of a longitudinally reciprocable shaft disposed within a sleeve shaft, said bearing comprising a pair of spaced relatively movable sleeve bushings disposed concentrically between said shafts, said sleeve bushings surrounding said reciprocable shaft and having inner and outer bearing surfaces engageable with the respective shafts, whereby said sleeve bushings isolate the space between said bushings and said shafts from the area above and below the respective sleeve bushing, each of said sleeve bushings having spaced peripheral grooves disposed adjacent to said longitudinally reciprocable shaft, the space between said shafts and said bushings defining a lubricant chamber adapted to receive a quantity of lubricant under pressure, and each of said sleeve bushings including means defining lubricant passages communicating with said peripheral grooves for conveying lubricant from said chamber to said peripheral grooves for lubricating the bearing surfaces of said sleeve bushings.

5. A pilot bearing for maintaining the concentric alignment of a longitudinally reciprocable shaft disposed within a sleeve shaft, said bearing comprising a pair of spaced relatively movable sleeve bushings disposed concentrically between said shafts, said sleeve bushings surrounding said reciprocable shaft and having inner and outer bearing surfaces engageable with the respective shafts whereby said sleeve bushings isolate the space between said bushings and said shafts from the area above and below the respective sleeve bushing, each of said sleeve bushings 7 having spaced peripheral grooves disposed adjacent to said longitudinally reciprocable shaft, the space between said shafts and said bushings defining a lubricant chamber adapted to receive a quantity of lubricant under pressure, said sleeve bushings being adapted to have an external fluid pressure applied to the ends thereof for relatively moving said sleeve bushings toward each other for maintaining the pressure of said lubricant substantially equal to said external fluid pressure, and each of said sleeve bushings including means defining lubricant passages communicating With said peripheral grooves for conveying lubricant from said chamber to said periph eral grooves for lubricating the bearing surfaces of said sleeve bushings.

6. A pilot bearing adapted for use between a pair of telescoping shafts of a drill string of an earth bore drilling apparatus wherein one of the shafts is disposed within and vibrates longitudinally relative to the other and the drill string is adapted to have mud fluid forced downwardly therethrough and upwardly between the drill string and the inner periphery of the earth bore in order to carry away chips of the earth formation at the bottom of the bore and cut away by the drilling apparatus, said bearing comprising a pair of spaced relatively movable sleeve bushings disposed concentrically between said shafts, said sleeve bushings surrounding said inner telescoping shaft and having inner and outer bearing surfaces engageable with the respective shafts whereby said sleeve bushings isolate the space between said bushings and said shafts from the area above and below the respective sleeve bushing, each of said sleeve bushings having spaced peripheral grooves disposed adjacent to said longitudinally reciprocable shaft, the space between said shafts and said bushings defining a lubricant chamber adapted to receive a quantity of lubricant under pressure, and each of said sleeve bushings including means defining lubricant passages communicating with said peripheral grooves for conveying lubricant from said chamber to said peripheral grooves for lubricating the bearing surfaces of said sleeve bushings.

7. A pilot bearing adapted for use between a pair of telescoping shafts of a drill string of an earth bore drilling apparatus wherein one of the shafts is disposed within and vibrates longitudinally relative to the other and the drill string is adapted to have mud fluid forced downwardly therethrough and upwardly between the drill string and the inner periphery of the earth bore in order to carry away chips of the earth formation at the bottom of the bore and cut away by the drilling apparatus, said bearing comprising a pair of spaced relatively movable sleeve bushings disposed concentrically between said shafts, said sleeve bushings surrounding said inner telescoping shaft and having inner and outer bearing surfaces engageable with the respective shafts whereby said sleeve bushings isolate the space between said bushings and said shafts from the area above and below the respective sleeve bushing, each of said sleeve bushings having spaced peripheral grooves disposed adjacent to said longitudinally reciprocable shaft, the space between said shafts and said bushings defining a lubricant chamber adapted to receive a quantity of lubricant under pressure, said sleeve bushings being adapted to be disposed between said shafts so that the mud fluid pressure is applied to the ends thereof for moving said sleeve bushings toward each other for maintaining the pressure of said lubricant substantially equal to said mud fluid pressure, and each of said sleeve bushings including means defining lubricant passages communicating with said peripheral grooves for lubricating the bearing surfaces of said sleeve bushings.

References Cited in the file of this patent UNITED STATES PATENTS I 687,067 Rigby Nov. 19, 1901 1,436,881 Kerr Nov. 28, 1922 1,457,181 Mable May 29, 1923 1,753,339 Hencken Apr. 8, 1930 2,670,928 Wagner Mar. 2, 1954 

